\documentclass[border=10pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\usepackage{amsmath}
\usepackage{environ}
\NewEnviron{scaledaligned}{
  \scalebox{1.5}{$\begin{aligned}
  \BODY
  \end{aligned}$}
}

% ensures a white background in the converted image
\pagecolor{white}

\begin{document}
\begin{tikzpicture}
  % draw fills so lines sit on top of them
  \fill [fill=black!70!white] (10, 0) rectangle (20, 1);
  \fill [fill=black!30!white] (0, 0) rectangle (10, 1);
  % outlines
  \draw [ultra thick] (0, 0) rectangle (20, 1);
  \draw [ultra thick, dashed] (10, 0) -- (10, 1);
  % material labels
  \node [fill=white] at (5, 0.5) {\scalebox{1.5}{Stainless Steel}};
  \node [fill=white] at (15, 0.5) {\scalebox{1.5}{Graphite}};
  % edge position markers and boundary conditions
  \node at (-0.57, -1.4) {
    \begin{scaledaligned}
      x &= 0 \\ \\
      T_S (0) &= 300
    \end{scaledaligned}
  };
  \node at (19.43, -1.4) {
    \begin{scaledaligned}
       x &= 2 \\ \\
       T_G (2) &= 300
     \end{scaledaligned}
  };
  % interface position marker and interface conditions
  \node at (10.95, -4.2) {
      \begin{scaledaligned}
        x &= 1 \\ \\
        -k_S \left. \frac{\text{d} T_S}{\text{d} x} \right|_{x = 1} &= q_c - q_e \\
        -k_G \left. \frac{\text{d} T_G}{\text{d} x} \right|_{x = 1} &= q_c + q_e \\[0.75cm]
        q_c &= C_T \left( T_S (1) - T_G (1) \right) \\
        q_e &= \frac{C_E}{2} \left( \phi_S (1) - \phi_G(1) \right)^2
      \end{scaledaligned}
  };
\end{tikzpicture}
\end{document}
